Antiviral STANDs (Avs) are bacterial anti-phage proteins that are considered as the evolutionary ancestors of immune pattern-recognition receptors of the NLR family. Following the recognition of a conserved phage protein, Avs proteins exhibit cellular toxicity and abort phage propagation by killing the infected cell. Type 2 Avs proteins (Avs2) were suggested to recognize the large terminase subunit of the phage by direct binding as a signature of phage infection based on co-expression assays. Here, we analyzed the binding partners of a type 2 Avs protein from Klebsiella pneumoniae (KpAvs2) expressed in Escherichia coli. Previous analysis revealed that, during phage SECphi18 infection, KpAvs2 recognized a small protein of unknown function, Ksap1. We repeated the experiment with a SECphi18 phage mutated for Ksap1 to see if KpAvs2 could recognize other proteins, such as the terminase, in absence of Ksap1.